(1) Field of the Invention
The present invention relates to a data locking mechanism for concurrent processes executing on networked processors. The invention has particular application within a submarine combat system. The inventive data locking mechanism is called "token migration" and takes advantage of the processing structure of submarine combat systems. Token migration like many other techniques allows at most one process in at most one processor to lock and access any data item.
(2) Description of the Prior Art
A prior art system dealing with communications disclosed by Coden in U.S. Pat. No. 4,789,982 describes a method for simulating a token passing ring network on a bus network. In operation, one node on receiving the token transmits data and then regenerates the token.
Another prior art system dealing with communications disclosed by Akai in U.S. Pat. No. 4,903,190 discloses a method of data transmission for a logical ring processor system which enables a processor to access internal memory of the processors which are not normally directly accessible from the data transmission loop. One portion of each common memory is reserved for a command signal transmitted on the transmission loop. Data from the internal memory of one of the processors is made available only when the command signal from another processor is received. In order to avoid data locking the common network memory increases as the square of the number of processors.
Hirabayashi et al. in U.S. Pat. No. 4,949,083 discloses a communication system which passes a token to each control unit which then may reject the token or may send data over the common transmission line. In either case, the token is then directed to continue on its preset transfer sequence.
Mansfield et al. in U.S. Pat. No. 5,014,192 discloses a data management system for multiprocessor systems connected in a logical ring configuration. A token is passed throughout the system. When a processor received the token it may send a frame of data or pass the token to the next processor. Although the system deals with satisfying a request for files in a network distributed file system connected as a logical ring there is no discussion of a data locking mechanism.